From: "Christopher Friesen" <cfriesen@nortelnetworks.com>
To: Gabriel Paubert <paubert@iram.es>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] (comments requested) adding finer-grained timing to PPC add_timer_randomness()
Date: Fri, 24 Aug 2001 09:59:39 -0400 [thread overview]
Message-ID: <3B865DCB.C60525B@nortelnetworks.com> (raw)
In-Reply-To: <Pine.LNX.4.21.0108240856370.1353-100000@ltgp.iram.es>
Gabriel Paubert wrote:
> No, both the RTC and the decrementer count nanoseconds, except that the 7
> LSB are not implemented because the timebase clock should have a period of
> 128 ns (7.8125 MHz, but according to Takashi Oe, many 601 systems did not
> bother to provide the exact frequency and are off by 11 parts in 4096 or
> so). As such the LSB can't be used to estimate randomness and the value
> must be shifted right by 7. So you need some conditional code (or boot
> time patching). At this point you can throw in the high order part
> (RTCU/TBU) for additional randomization (RTCU changes much faster on 601,
> once per second, than on the other processors).
Have you got any links to information on boot time patching?
--
Chris Friesen | MailStop: 043/33/F10
Nortel Networks | work: (613) 765-0557
3500 Carling Avenue | fax: (613) 765-2986
Nepean, ON K2H 8E9 Canada | email: cfriesen@nortelnetworks.com
next prev parent reply other threads:[~2001-08-28 19:45 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-08-22 20:57 [PATCH] (comments requested) adding finer-grained timing to PPC add_timer_randomness() Chris Friesen
2001-08-22 21:06 ` Ignacio Vazquez-Abrams
2001-08-22 21:27 ` Chris Friesen
2001-08-23 1:33 ` Paul Mackerras
2001-08-23 9:46 ` Gabriel Paubert
2001-08-23 13:11 ` Benjamin Herrenschmidt
2001-08-23 12:31 ` Paul Mackerras
2001-08-24 7:32 ` Gabriel Paubert
2001-08-24 13:59 ` Christopher Friesen [this message]
2001-08-28 20:50 ` Gabriel Paubert
2001-08-24 17:54 ` [PATCH] (comments requested) adding finer-grained timing to PPC Albert D. Cahalan
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